Color filters used in liquid crystal displays are members that enable color display on a display by allowing the color filters to transmit white light from a backlight. Among these, there is a need for increased brightness and a widened color reproduction range in green coloring agents for color filters.
Selecting a pigment with high transmittance with respect to the light from the backlight is important for increasing brightness and improvements have been made using Pigment Green 58 as a main pigment instead of the conventionally used Pigment Green 36. In addition, by increasing the brightness of the pigment, the white light from the backlight can be used effectively and, as a result, energy savings and reductions in manufacturing costs of displays are possible.
Furthermore, in order to widen the color reproduction range, Pigment Green 7 with which film thickness for a specific chromaticity can be reduced as compared to Pigment Green 36 and Pigment Green 58, is selected as the main pigment. The reason why Pigment Green 7 is selected is because while it is possible to widen the color reproduction range by increasing film thickness of Pigment Green 36 or Pigment Green 58, it is not possible to attain an NTSC ratio of 90% or higher with a practical film thickness. For example, proposals have been made for forming green pixels using a green photosensitive resin composition containing Pigment Green 7 and Pigment Yellow 185, and achieving a film thickness of 2.2 μm or less and high color reproduction. However, due to the fact that the transmittance of Pigment Green 7 is low as compared to that of Pigment Green 36 and Pigment Green 58, there is a problem in that the brightness of the resulting display decreases. Furthermore, while it is possible to compensate for the brightness by increasing the light intensity of the backlight, this leads to a new problem in that the amount of power consumption increases. As such, there is a demand for improvement. Thus, there is a need for a color material for color filters by which both brightness and color reproducibility can be achieved.
To solve the problems described above, PTL 1 and PTL 2 propose the use of a color material constituted from Pigment Green 58, Pigment Blue 15:3 and/or Pigment Blue 15:6 as a blue color material, and Pigment Yellow 150 as a yellow pigment.
PTL 3 proposes that brightness can be improved through the use of a color material including Pigment Green 7 as a green pigment, Pigment Yellow 138 as a yellow pigment, and a yellow dye.
Furthermore, PTL 4 to PTL 6 propose a pigment for color filters containing a halogenated zinc phthalocyanine in which numbers of bromine atoms, chlorine atoms, and hydrogen atoms are specified, and capable of displaying certain chromatic coordinates of yellow.
However, the background art is not sufficient and currently incapable of forming a color filter aimed at increasing brightness and expanding the color reproduction range.